Induction controlled mine firing mechanism



W. R. MALTBY INDUCTION CONTROLLED MINE FIRING MECHANISM Filed April 13, 1948 June 26, 1962 vvvvvvvvvv tats V 3,d4@,658 Patentedlune 26, 1962 possibility of exploding the mine by an airborne mine sweeping operation is remote. More specifically, the present invention contemplates the provision of means for detecting, at predetermined spaced intervals, changes detected within these intervals.

The types of induction mines heretofore devised have been swept by airborne mine sweeping apparatus compris- In the system of the present invention, the mine firing mechanism includes certain detecting, selecting and time delay elements in combination with the field sensing device whereby the detonation of the mine is efiected when of a second changing magnetic condition within a predetermined time interval immediately following the dead interval.

By reason of the selecting and time delay elements and circuit connections therebetween, thedetonation of the scription proceeds.

One of the objects of the present invention is to provide a new and improved magnetic mine firing mechanism of simple and rugged construction which is selectively responsive to a changing magnetic field which will be sired qualities of reliability and efiiciency in use and operation.

responsive to a changing magnetic field for comparing the continuance of the changing field with a predetermined interval of time and selectively firing an explosive nection with the following drawing, of Which:

FIG. 1 is a view of the mine employing the mine firing circuit of the present invention and showing an airborne sweeping operation thereof, and

. 2 is a circuit diagram showing in schematic form means such, for example, as a copper slug or the dash pot 6 illustrated to render the relay slow in releasing clock indicated arming contacts are closed has been discharged by the operation of relay :2 r a purpose which will be more clearly apparent as the :scription proceeds. A time delay device TD is also rovided in which the operating magnet thereof is adapted attract a rotatable armature 7 and cause it to move way from a stop 8 against which it is yieldably urged y a spring 9. The rate of movement of the armature 7 s retarded by an escapement mechanism such that the xperating magnet of the time delay device is required to :e energized continuously for a predetermined period of :ime such, for example, as 10 seconds before the armature 7 has moved through a distance sufficient to close the normally open contacts 11 of the device. The time delay device is connected in series with the winding of relay R and is set into operation when the operating circuit to relay R is closed. In the event that the operating circuit to relay R and the timing device does not remain closed for the period of time required to close contacts 11, the interruption of this circuit causes armature '7 to be quickly restored by the spring 9 to the initial unoperated position thereof in engagement with the stop 8. The power required for the operation of relay R and the time delay device TD is obtained from a battery B, the circuit including a pair of contacts on an arming generally by the numeral 12. The arming clock may be of any type for the purpose in which the clock is set in operation by a hydrostatic device actuated by the pressure of the water within which the mine is planted, as is well known in the art to which the present invention pertains.

Whereas in FIG. 2 there is shown an arming clock 12 having a pair of normally open contacts adapted to be closed within a predetermined period of time such, for example, as minutes after the mine has been planted it will, of course, be understood that various other well known arrangements may be employed for arming the mine such, for example, as an arrangement in which the by a hydrostat when sufficient time has elapsed for a soluble washer asosciated therewith to become dissolved and thereby permit movement of the hydrostat.

The mine firing mechanism of FIG. 2 also includes a battery B1 connected in series with battery B for charging a condenser C through a pair of resistance elements 13 and 14. The ohmic value of the resistance elements 13 and 14 bears a predetermined relation with respect to the capacity of condenser C such that a predetermined period of time such, for example, as 60 seconds is re- .quired to charge the condenser C fully after the condenser R. The condenser C is employed to provide a source of stored electrical energy sufficient to operate the reset magnet DR of relay D as the contacts of relay R are closed and to maintain the magnet DR operated for a predetermined interval of time such as two seconds. This is accomplished by providing a winding of the reset magnet DR of sufficient resistance to prevent discharging the condenser to a value below the hold valve of the magnet DR during this interval. Each time the reset magnet DR is operated by relay R the charge on condenser C is exhausted and does not build up again until a predetermined period of time such, for example, as 60 seconds has elapsed after relay R has released whereby, in the event that relay D is operated by the voltage from the pickup coil in response to a changing magnetic field before the charge on the condenser has built up to a value sufficient to operate the reset magnet DR, relay D remains operated for a period of time sufficient to cause contacts 11 of the time delay device TD to close and fire the electroresponsive detonator 15.

The operation of the system will best be understood by consideration of a specific example. Let it be assumed by way of example that the mine has been planted within the body of water and that the contacts of relay D are moved to the closed position thereof during the planting operation.

When the mine has been planted for a period of time sequently passes above the mine.

.thereof in the original unoperated position.

suflicient for the contacts of the arming clock 12 to close, a circuit is completed from the positive terminal of battery B by way of conductor 16, contacts of arming clock 12, conductor 17, contacts of relay D, conductor 18, winding of relay R, conductor 19, operating winding of time delay device TD, from whence the circuit is continued by way of conductor 21 to the negative terminal of battery B thereby causing relay R to operate and the time delay device TD to be set into operation. As armature 22 of relay R is moved into engagement with its contact, a circuit is closed from the positively charged plate of condenser C by way of conductor 23, reset magnet DR of relay D, conductor 24, make contact and armature 22 of relay R, conductor 25, and thence to the negative plate of condenser C When this occurs the charge on condenser C causes the reset magnet DR to operate and forcibly restore the moving contact element of relay D to a position intermediate the pair of contacts of the relay and disengaged therefrom, the moving contact element being locked in this position until the reset magnet is released. During this period of restraint of the relay D the mine is disarmed.

As the contacts of relay D are disengaged, the operating circiut to relay R and time delay device TD is interrupted delay device TD immediately restores to normal. Armature 22 of relay R, however, is prevented from disengaging its make contact until a period of time sufficient to discharge condenser C such, for example, as four seconds has elapsed by reason of the provision of the dash pot 6 thereon. As armature 22 of relay R is disengaged from its make contact, the operating circuit for reset magnet DR is interrupted, the reset magnet is released, the restraint of the movable element of relay D is removed and relay D is responsive to a change in the ambient magnetic field detected by the pickup coil SC. The mine is now armed. The release of relay R at armature 22 thereof removes the discharge load from condenser C and the condenser now receives a charging current from batteries B and B1 by way of resistances 13 and 14. When condenser C has become fully charged the charging current from batteries B and B1 ceases.

Let it now be assumed that a steel vessel or a vessel having a preponderance of magnetic material therein sub- As relay D operates in response to the first changing condition of the magnetic field caused by the moving vessel, a circuit is closed to operate relay R and set the time delay device TD into operation. As armature 22 of relay R engages its contact, condenser C is connected to the reset magnet DR over a closed circuit and the reset magnet operates thereby restoring and locking relay D with the movable contact remains locked until the charge on condenser C has decerased sufiiciently to release the magnet DR. While relay D is thus locked, the mine is disarmed and unresponsive to changes in the magnetic field.

As relay D releases, the operating circuit to relay R and 1 the time delay device TD is interrupted and the time ond signal received from the pickup thereby rearming the mine.

delay device is restored to normal by the spring 9. Relay R releases in time delayed relation with respect to the interruption of the operating circuit thereto by reason of the provision of the dash pot 6 aforesaid or other time delay means provided thereon and the reset magnet DR is disconnected from condenser C. When this occurs the load is removed from condenser C and the condenser be- The removal of restraint from relay D as magnet DR releases renders relay D responsive to a secor search coil SC It may now be assumed that the relay D operates a second time by reason of the changing magnetic fiel caused by the vessel moving above the mine and detected by the pickup coil SC. As the contacts of relay D are engaged, relay R operates and the time delay device TD is set into operation. As armature 22 of relay R is moved to closed position, condenser C is connected to the reset ductor 16, closed contacts 12 of the arming clock, conteachings. It is, the scope of the appended claims the'inventionmay be Letters Patent of the United States is:

In a submarine mine of the character disclosed arranged within a magnetic field, a relay, means including said relay for detecting a plurality of changing magnetic named relay lay for closing said discharge circuit thereby to operate discharged.

2. In a submarine ranged within a magnetic field, an electrical relay, means condition has been'detected, said last-named means including a condenser, a normally open discharge circuit for said condenser and condenser, a charging circuit for said condenser operatively connected to sald source of power and having resistance ing condition scharge the condenser, a device adapted to measure a 'edetermined interval of time in excess of the discharge ne of the condenser, said device being connected to said :lay and operated thereby, a mine firing circuit, and leans on said device for closing said mine firing circuit hen the time delay device has measured said predeteriined interval of time in response to a second changing nagnetic condition within said field sensed by said sensing neans while the condenser is being charged and before he charge on the condenser has become sufiicient to iperate the relay restoring and locking means.

7. In a marine mine of the character disclosed, in combination, a mine firing mechanism disposed within a magnetic field, means in said firing mechanism for sensing in succession a plurality of changing conditions in said field during different intervals of time, a relay connected to said sensing means and adapted to be operated thereby as a changing condition is sensed, condenser means controlled by said relay for rendering the relay unresponsive to said sensing means for a predetermined period of time intermediate two of said time intervals when a changing magnetic condition has been sensed within the first of said intervals, means controlled by said condenser for measuring said second interval whereby the time of occurrence of a second changing condition sensed by said sensing means is compared with said second interval, and means controlled by said relay for firing the mine selectively in accordance with said comparison whereby the mine is fired when the second changis sensed within said second interval.

adapted to be disposed within a magnetic field, means for detecting changing magnetic conditions within said field, a first relay means responsive to detection of a changed magnetic condition by said first-named means, a condenser, circuit means including a source of potential for slowly charging said condenser, means 8. In a mine including a second relay connected in the discharge path circuit for said condenser for resetting and locking said relay means for a predetermined period of time, a third relay means, said last-named relay means being actuated by said relay means and operable to discharge said condenser, and time delay means energized by said first relay means for firing the mine whereby after detection of an initial change in the magnetic field the first relay means is rendered unresponsive to a second change in the magnetic field during said predetermined period of time and the mine is fired upon detection of a change in the magnetic field within the time interval required for charging said condenser after the expiration of said predetermined period of time.

9. In a submarine mine posed within a magnetic field, a sensitive 0nd relay connected for operation thereby, cuit means including said sensitive relay for detecting in succession a plurality of changing magnetic conditions within said field occurring during ditferent intervals of time, means including a normally charged condenser connected for controlled discharge of the condenser by said second relay for locking said sensitive relay in a released condition for a predetermined period of time intermediate two of said time intervals when a changing magnetic condition has been detected within the first of said intervals, and means including a time delay relay connected in series of the character disclosed disrelay and a secdetector cirwith said second relay for firing the mine when a changing magnetic condition within the field has been detected during the second one of said intervals.

References Cited in the file of this patent 2,400,549 Glennon et al 

